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In this paper, authors established a farmer crop selection model (FCS) for the three provinces of Liaoning, Jilin and Heilongjiang of the Northeast China
. With linking to the environmental policy integrated climate model (EPIC), the simulated results of FCS model for maize, rice and soybean were spatialized with 1 km×1 km grids to obtain cropping pattern. The reference map of spatial distribution for the three staple crops acquired by remote sensing imageries was applied to validate the simulated cropping pattern. The results showed that (1) the total simulation accuracy for the study area was 78.62%, which proved simulation method was applicable and feasible; (2) simulation accuracy for Jilin Province was the highest among the three provinces with a rate of 82.45% since its simple cropping system and not complex topography; (3) simulation accuracy for maize was the best among the three staple crops with a ratio of 81.14% because the study area is very suitable for maize growth. We hope this study could provide the reference for cropping pattern forecasting and decision-making
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The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly
. The Absorption Angstrom Exponent (AAE) method has been widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosols, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the AAE method was applied to both urban and rural environments in the Pearl River Delta (PRD) region of China, with an improvement of constraining the realistic AAE of "pure" BC through statistical analysis of on-line measurement data. A three-wavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that more realistic AAE values for "pure" BC aerosol (AAEBC) were 0.86, 0.82, and 1.02 between 405 and 781?nm, and 0.70, 0.71, and 0.86 between 532 and 781?nm, in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively. Roadway tunnel experiments were conducted and the results further confirmed the representativeness of the obtained AAEBC values for the urban environment. Finally, the average light absorption contributions of BrC (±?relative uncertainties) at 405?nm were quantified to be 11.7?% (±5?%), 6.3?% (±4?%), and 12.1?% (±7?%) in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively, and those at 532?nm were 10.0?% (±2?%), 4.1?% (±3?%), and 5.5?% (±5?%), respectively. The relatively higher BrC absorption contribution at 405?nm in the ruralfall campaign could be reasonably attributed to the biomass burning events nearby, which was then directly supported by the biomass burning simulation experiments performed in this study. This paper indicates that the BrC contribution to total aerosol light absorption at shorter wavelengths is not negligible in the highly urbanized and industrialized PRD region
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Methane fluxes from a shallow peatland lake (3450 m a
.s.l., 1.6 km2 in area, maximum depth < 1 m) on eastern Tibetan Plateau were measured with floating chamber method during May to August, 2009. The overall average of methane emission rate during the study period was 34.71 ± 29.15 mg CH4 m− 2 h− 1. The occurrence of ebullition among the overall methane flux from Lake Medo was about 74%. The average rate of ebullition was 32.45 ± 28.31 mg CH4 m− 2 h− 1, which accounted for 93% of the overall average of methane emission. Significant seasonal variation was found for occurrence (P < 0.05) and rate (P < 0.01) of ebullition, both peaking synchronously in mid-summer. Both the occurrence and rate of ebullition were found positively related to sediment temperature but negatively related to lake water depth. The high methane production in the lake sediment was likely fueled by organic carbon loaded from surrounding peatlands to the lake. The shallowness of the water column could be another important favorable factor for methane-containing bubble formation in the sediment and their transportation to the atmosphere. The methane ebullition must have been enhanced by the low atmospheric pressure (ca. 672 hPa) in the high-altitude environment. For a better understanding on the mechanism of methane emission from alpine lakes, more lakes on the Tibetan Plateau should be studied in the future for their methane ebullition
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We measured nitrous oxide (N2O) emission from the infralittoral zone and pelagic zone in a shallow lake on the Tibetan Plateau during the growing season of 2009, prior to the lake restoration project aiming to raise the lake water by 0
.5–1 m. Mean flux rates of N2O were 0.054 ± 0.094 mg N2O m−2 h−1 and 0.009 ± 0.072 mg N2O m−2 h−1 from infralittoral zone and pelagic zone respectively. Submerged plant biomass index (SPBI) (R = 0.43, P < 0.01, n = 16), nitrate content in surface sediment (R = 0.22, P < 0.05, n = 16) and surface sediment temperature (R = 0.79, P = 0.000, n = 16) were found to significantly correlated to the spatial pattern of N2O flux. Nitrates loading gradient across (sub) zones along with the enhancing effect of plant on nitrate removal were thought to be responsible for this spatial pattern of N2O flux, while temperature act as a regulator on denitrification. Infralittoral zone had the greatest relative contribution (62.2%) of N2O emission to the whole lake budget among various (sub) zones, indicating infralittoral zone a vital component of N2O emission from shallow lakes. As the consequence of the lake restoration project, the response of N2O flux to the raised water depth might vary from different (sub) zones, therefore further study should be conducted so as to have a better understanding on the effect of restoration project on the overall N2O flux from the lake
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Zhu, D.; Wu, N.; Bhattarai, N.; Oli, K. P.; Tsering, K.; Rawat, G. S.; Chen, H.; Yang, G.; He, Y.; Joshi, S.; Rana, P.; Ismail, M.
Natural wetlands constitute one of the major sources of methane emission to the atmosphere
. Data on methane emission from wetlands on southern slopes of the Himalaya (SSH) have not been reported so far. Such data are very valuable for filling the gap and generating the whole emission patterns at regional or even global scale. We selected two wetlands at different altitudinal locations in Nepal, i.e. Beeshazar Lake (286 m a.s.l.) and Dhaap Lake (2089 m a.s.l.), to monitor the daytime methane emissions in monsoon season and dry season separately. Daytime methane emission varied between monsoon and dry seasons and also across different plant communities. The daytime methane emission variations were stronger in dry season than in monsoon season. The source/sink strengths of the two selected plant communities in each wetland were significantly different, presenting the strong spatial variation of methane emission within wetland. The methane emissions recorded in monsoon season were significantly higher (7.74 ± 6.49 mg CH4 m−2 h−1 and 1.00 ± 1.23 mg CH4 m−2 h−1 in low and high altitude wetlands, respectively) than those in dry season (1.84 ± 4.57 mg CH4 m−2 h−1 and 0.27 ± 0.71 mg CH4 m−2 h−1 in low and high altitude wetlands, respectively). Methane emissions from the low altitude wetland were significantly higher than those from the high altitude wetland in both of the seasons. Plant community height, standing water depth and soil temperature correlated to the methane emission from wetlands in this region
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Wang, M.; Yang, G.; Gao, Y.; Chen, H.; Wu, N.; Peng, C.; Zhu, Q.; Zhu, D.; Wu, J.; He, Y.; Tian, J.; Zhao, X.; Zhang, Y.
In order to understand the carbon fate of alpine peatlands under climate change, this study aimed to measure carbon accumulation in recent decades and that during the Holocene at seven representative peat sites on the Zoige Plateau using empirical peat core data (14C and 137CS) and modeling approaches
. The observed apparent carbon accumulation rate over the past 50 years was 75 (35–123) g C m−2 yr−1, nearly four times that of 19 (7–30) g C m−2 yr−1over the whole Holocene. With decomposition history included in consideration by using modeling approaches, the average expected peat carbon accumulation rate was still nearly 1.6 times that of the modeled net carbon uptake rate of peats accumulated over the whole Holocene, though exceptions were found for Denahequ and Hongyuan peat cores with extremely low water table levels. The newly accumulated peat carbon of the Zoige Plateau amounted to 0.4 Tg C yr−1 (1 Tg = 1012 g) during recent decades. Overall, the effect of climate warming on recent C accumulation of peatlands on the Zoige Plateau is dependent on their water conditions. The peat C storage on the alpine Plateau is threatened by human activities (drainage) and continuous climate change with increasing temperature and decreasing precipitation which cause dryness of peatlands
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Wang, M.; Chen, H.; Wu, N.; Peng, C.; Zhu, Q.; Zhu, D.; Yang, G.; Wu, J.; He, Y.; Gao, Y.; Tian, J.; Zhao, X.
Understanding the responses of the carbon-rich peatland ecosystems to past climate change is crucial for predicting peat carbon fate in the future
. Here we presented a data synthesis of peatland initiation ages, area changes, and peat carbon (C) accumulation rate variations in China since the Holocene, along with total C pool estimates. The data showed different controls of peatland expansion and C accumulation in different regions. The peat C accumulation rates were 32.3 (ranging from 20.7 to 50.2) g C m-2 yr-1 in the Qinghai-Tibetan Plateau (QTP) and 14.7 (ranging from 7.4 to 36.5) g C m-2 yr-1 in the Northeast China (NEC). The peaks of peatland expansion and C accumulation in the QTP occurred in the early Holocene in response to high summer insolation and strong summer-winter climate seasonality. The rapid peatland expansion and maximum C accumulation rate in the NEC occurred in the middle-late Holocene. Peatlands scattered in the coastal and lakeside regions of China expanded rapidly at the onset of the Holocene due to large transgression, consistent with the stronger summer insolation and monsoon, and during the middle and late Holocene, as a response to the high and stable sea level and the strong summer monsoon. The carbon storage of peatlands in China was estimated as 2.17 (ranging from 1.16 to 3.18) Pg, among which 1.49 (ranging from 0.58 to 2.40) Pg was contributed by peatlands in the QTP, 0.21 (ranging from 0.11 to 0.31) Pg by those in the NEC, and 0.47Pg by those scattered in other regions of China. Our comparison of peatlands dynamics among regions in China showed that climate and monsoon are the essential factors in determining the expansion and carbon accumulation patterns of peatlands, although their effects on peatland formation and C accumulation is complex owing to land availability in peatland basins and regional moisture conditions
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Wang, Y.; Chen, H.; Zhu, Q.; Peng, C.; Wu, N.; Yang, G.; Zhu, D.; Tian, J.; Tian, L.; Kang, X.; He, Y.; Gao, Y.; Zhao, X.
Sinks of methane (CH4) become highly variable due to both human activity and climate change
. An urgent need therefore exists to budget key sinks of CH4, such as forests and grasslands. In this study, CH4 uptake of forests and grasslands in China was first reviewed and then estimated based upon the review itself. Total uptake from the two CH4 sinks were 1.323TgCH4yr-1 in China (ranging from 0.567 to 2.078TgCH4yr-1), lower than a previous estimate in China (2.56TgCH4yr-1). Among the uptake, 0.650TgCH4yr-1 (ranging from 0.168 to 1.132TgCH4yr-1) was consumed by grasslands and 0.675TgCH4yr-1 (ranging from 0.399 to 0.946TgCH4yr-1) by forests. The largest CH4 uptake of grasslands was found in the Qinghai-Tibetan Plateau High-Frigid Domain, which consumed 0.284TgCH4yr-1, about 44% of the whole uptake of grasslands in China. The greatest CH4 uptake (0.553TgCH4yr-1) of forests took place in Eastern Humid and Semi-humid Domain of the country, which was about 82% of the total annual CH4 uptake of forests in China. With forests and grasslands taken together, Eastern Humid and Semi-humid Domain was the largest CH4 consumer, taking up about 0.715TgCH4yr-1, accounting for 82% of the whole forest uptake and 25% of the whole grassland uptake in China. On the ecoregion scale, due to extensive forest distribution and longer growing season, Southern Asia monsoon broadleaf forest ecoregion was the greatest CH4 uptake (0.320TgCH4yr-1) of forests and grasslands in China, consuming more CH4 than the Northeastern Arid and Semi-arid Domain combined. Our results indicated that forests and grasslands are not constant sinks of CH4 but decreasing ones influenced by climate change and anthropogenic activity. More field data, mechanism understanding and process-based models could help better estimate and understand CH4 uptakes of forests and grasslands in China. © 2014 Elsevier Ltd
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Annotation:::: The paper examines incentive factors and resettlement modes in mountain migration aimed at achieving comprehensive development of the mountain area
. Using a method of demographic analysis and documental study, the paper assesses the factors that affect mountain migration in Yunnan and suggest some relatively effective modes of migration.According to the findings, some incentive factors that affect mountain migration include resource availability, the construction of a project, and efforts to protect the environment. The relatively effective modes of migration include migration within the area and area-to-area migration. Lastly, eco-migration and project-related migration are the most frequently adopted methods of mountain migration in Yunnan provinc
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Climatic data, ice core records, the tree ring index, and recorded glacier variations have been used to reconstruct a history of climatic and glacial changes in the monsoonal temperate glacier region of southwestern China during the last 400 years
. The region's temperature has increased in a fluctuating manner during the twentieth century after two cold stages of the Little Ice Age (seventeenth to nineteenth centuries), with a corresponding retreat of most of the glaciers, against a background of global warming. Retreat rates accelerated after the 1980s. The few advancing glaciers that did exist have started to retreat in recent years. The amount, trend, and amplitude of variation of precipitation have differed in different parts of the region. The Dasuopu ice core, from the western part of the region, shows a decreasing trend in precipitation, the converse of the trend in temperature. In the eastern part of the region, however, a rising trend of rainfall has accompanied increasing temperatures as a result of the variable atmospheric circulations from different sources. The southwest monsoon, the principal controlling factor in the Chinese monsoonal temperate glacier region, can be classified into the Indian monsoon and the Bengal monsoon. The former passes across the Indian Peninsula from the Arabian Sea and transports vapor for precipitation in the western part of the monsoonal temperate glacier region. The Bengal monsoon, originating in the Bay of Bengal, is the major source of precipitation in the eastern part of the region. The eastern part is also influenced by the southeast monsoon arriving from the western Pacific, and the western part is affected in winter by the southern branch of the westerly circulation. This complex atmospheric situation results in differing patterns of precipitation in the western and eastern zones. Although it is clear that both temperature and precipitation affect the glaciers, further work is needed to confirm which of these is the major factor influencing present glacier change. Copyright 2003 by the American Geophysical Union
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